Oil well pumping systems are well known in the art. Such systems are used to mechanically remove oil or other fluid from beneath the earth's surface, particularly when the natural pressure in an oil well has diminished. Generally, an oil well pumping system begins with an above-ground pumping unit, which can be commonly referred to as a “pumpjack,” “nodding donkey,” “horsehead pump,” “beam pump,” “sucker rod pump,” and the like. The pumping unit creates a reciprocating up and down pumping action that moves the oil or other substance being pumped out of the ground and into a flow line, from which the oil is then taken to a storage tank or other such structure.
Below the ground, a shaft is lined with piping known as “tubing.” Into the tubing is inserted a string of sucker rods, which ultimately is indirectly coupled at its north end to the above-ground pumping unit. The string of sucker rods is indirectly coupled at its south end to a subsurface pump that is located at or near the fluid in the oil well. The subsurface pump has a number of basic components, including a barrel and a plunger. The plunger operates within the barrel, and the barrel, in turn, is positioned within the tubing. It is common for the barrel to include a standing valve and the plunger to include a traveling valve. The north end of the plunger is typically connected to a valve rod, which moves up and down to actuate the pump plunger. The valve rod passes through a guide positioned at the north end of the barrel, which assists in centering the valve rod and thereby, the plunger. In addition, the guide includes openings through which the oil or other substance being pumped can exit the pump barrel and travel into the tubing.
There are a number of problems that can occur during oil pumping operations. Fluid that is pumped from the ground is generally impure, and includes solid impurities such as sand, pebbles, limestone, and other sediment and debris. Certain kinds of pumped fluids, such as heavy crude, tend to contain a relatively large amount of solids. Because of this, several disadvantages exist with prior valve rods. For example, after the solids have been exhausted from the pump barrel and the pump has temporarily discontinued pumping operations, the solids will naturally begin to settle due to gravity. With prior art valve rods, the solids are able to reenter the pump barrel at this time. This often results in excessive barrel wear upon restarting of the pump. Furthermore, it is possible that with the solids reentering the pump barrel, they can cause sticking of the pump i.e., seizing the plunger in the barrel.
Conventional pumps discharge fluid into the tubing allowing the fluid to move to the surface. On upstrokes, the well fluid through the pump discharges to the top valve rod guide. When the plunger moves downward back into the barrel, the open cage atop the pump allows fluid that was just discharged to reenter the barrel through the rod guide. The fluid discharged into the tubing from the pump contains solids that concentrate themselves into the first two or three joints of tubing due to gravity. The fluid contained in this section of tubing is concentrated and contains a higher percentage of solids than the fluid that was just discharged thus introducing additional solid impurities that create additional damage to both the barrel and plunger.
The present application relates to a sand check filter for use with conventional rod pumps for preventing or reducing the amount of solids from reentering back into the pump. It addresses the problems encountered in prior art pumping systems as well as provides other, related advantages.